Title

Author

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Dr. Andrew N. Hrymak

2nd Supervisor

Dr. Argyrios Margaritis

Co-Supervisor

Abstract

The aims of this study were to investigate the effect of culture conditions on the production of bacterial cellulose (BC) by Komagataeibacter xylinus (K. xylinus), to assess the feasibility of tailoring the surface properties of bacterial cellulose nanocrystals (BCNs) through the culture conditions, and to use the BCNs in an aqueous system for drug adsorption application. BC fibers production improved with increased agitation rates in a stirred tank bioreactor resulting in yields of 0.54 and 1.13 g of BC per litre at agitation rates of 500 rpm and 700 rpm, respectively. Separation and purification of bacterial cellulose were achieved in a one-step process, while also preserving the crystalline cellulose structure. Stirred-tank bioreactors represent a promising avenue for scale up to achieve high yields of bacterial cellulose.

A shake flask study was conducted to investigate the yield of BCNs in relation to the BC fibers production. Rotational speed significantly affected the production of BC fibers and yield of BCNs. It was observed that the highest BC production also generated the maximum total mass of BCNs per volume of the culture medium. The optimal medium that achieved the highest amount of BCNs contained 25 g of fructose l-1 and 35 g of CSS l-1 at a pH of 4.5, when cultivated in a rotary shaker incubator at 250 rpm.

BCNs obtained from sulfuric acid hydrolysis were used as an adsorbent for ionizable antibiotic tetracycline hydrochloride (TCH) from concentrated aqueous suspension. After 6 hours of adsorption, both pH and rotational speed did not significantly affect the adsorption capacity of antibiotic tetracycline hydrochloride (TCH) on BCNs, reaching a maximum loading of of TCH per gram of BCNs at and pH 3.

Modification of BC fibers production parameters increased the yield of BCNs and affected the BCNs size distribution. The adsorption kinetics of TCH on BCNs followed pseudo-second order kinetic model with a better fit on the higher BCNs dosage. In addition, this study demonstrates that bacterial-derived cellulose nanocrystals are an effective adsorbent for tetracycline hydrochloride drug delivery excipient in an aqueous system.